Rotary scanner



April 17, 1956 R. E. CLAPP ROTARY SCANNER 2 Sheets-Sheet 1 Filed Jan. 10, 1946 INVENTOR ROGER E. CLAPP ATTORNEY April 17, 1956 R. E. CLAPP 2,742,642

ROTARY SCANNER Filed Jan. 10, 1946 2 Sheets-Sheet 2 :ZZZZTZZZZ 2 iii:

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INVENTOR ROGER E. CLAPP FIG. 3

ROTARY SCANNER Rage E- Clapp, Cambridge, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy .1 Application January 10, 1946, Serial No. 640,280

' 9 Claims. Cl. 343-454 1 This invention relates in general to antenna systems and more particularly to a simplified rotary type of scanner. The present invention represents an improvement of the scanner reported'in copending application entitled, Antenna Systems with Variable Directional Characteristics,*file'd- November 10, 1943, Serial No. 509,790, now Paten-t' No. 2,605,413. In the aforesaid'copending application a radar scanner produced a swinging curtain type of radar beam, which is, broadly speaking, a beam of eie'ctromagnetic energy of relatively low directivity in one plane but'of'relatively high directivity in a direction perpendicular to the plane and which is adapted to be varied'in orientation about a line in the plane of low directivity. This was accomplished by a linear array of dipoies disposed along a waveguide, the width of the waveguide being varied. This variation caused the wavelength within the guide to change, and in this manner the phaseof the electromagnetic energy at the respective dipoles also varied so as to produce the desired motion of the radar beam. The aforesaid type of scanner is frequently referred to as a delta-A type of scanner because of'th e fact that the A dimension of the guide is given incremental variations.

The general principles disclosed in the above identified application, that is the variation of the broad dimension of-a waveguide in order to change the phasing of electromagnetic energy at a series of dipoles, have been incorporated 'into the present invention, with a novel and improved mechanical arrangement for producing such variation. Reference is made to the aforesaid copending application for an earlier mechanical arrangement in which one wall of a'waveguide was given a reciprocating motion for the scanning operation.

The principal object of this invention is to provide a rotary scanner designed to sweep a beam of electromagnetic energy.

Another object of this invention is to provide in a rotary scanner means for mechanically varying the A -dimension of a variable dimension waveguide.

Afurther object of this invention is to provide means for simultaneously propagating and sweeping a plurality of beams of electromagnetic energy.

Thes'e'and other objects will be apparent from the following specification when taken with the accompanying drawings, in which 2' Fig. 1 is a longitudinal view, partly in section, of an embodiment of the invention;

Fig. 2 is a cross section of the embodiment shown in Fig. 1 taken on the plane II-II of Fig. 1; and

Fig. 3 is a schematic diagram illustrating the operation of the embodiment of Figs. I and 2.

In Fig. I inner-assembly 3i) including, a hollow cylindrical conductivernember 31 with a plurality of externally projecting vanes 13 and 17 of similar conductive material arranged in a plurality of arrarys, is free to rotate with respect tothe outer assembly 20, including, a second hollow cylindrical conductive member--21 having a plurality of internally projecting vanes 12 and 14 of similar atetrt 2. conductive material arranged in plurality of arrays. The mechanical arrangement is such that the'sets of vanes 13 and 17 on the'inner assembly 30 can pass through the sets of vanes 12 and 14 within the outer assembly 20.

A rectangular wave guide 40, terminated by coupling plate 41 provides a means for feeding the rotary scanner.

Fig. 2 is a cross section of the embodiment shown in Fig. 1 taken in the plane II--II of Fig. 1 and Fig. 3 is a schematic drawing showing all of the movable and stationary vane arrays revolved into the plane of the drawing. Figs. 2 and 3 illustrate the relation of the inner rotating assembly 30 to the outer-stationary assembly 20 and the formation of. variable" dimension waveguide 25 by the aforesaid assemblies 20 and 30. It should be noted'that for purposes of illustration vane array14B" is represented twicev in the schematic diagram of Fig. 3 to indicate more clearly that each of the rotatable vane arrays 17, 13, and 15 cyclically passes through the stationary vane arrays 14B, 14A, 14, and 12 in the order named. The rotation of inner member 30 provides the desired periodic variation in the broad or A dimension of the waveguide 25.

The axial dipole array 11 is fed by the electromagnetic energy, through openings (not shown) in waveguide 25 comprising the separation between vane array 12 and vane array 13. By way of illustration, let it be assumed that inner assembly 30, comprising the vane arrays 13, 15' and 17, rotates continuously in the direction of the arrows (Figs. 2 and 3). The mechanical drive is not shown. As a waveguide 25,. is narrowed due to vanes 13 approaching vanes 12, the phasing of the electromagnetic energy at dipole array 11 will be changed and a scanning beam of electromagnetic energy will be obtained.

After waveguide 25 has been narrowed below cutoff, no power will be radiated for a certain time interval. When vane array 13 passes beyond dipole array 11 and then passes through vane array 12, the efiective width of waveguide 25 will again be the maximum width, namely the separation between vanes 12 and 14. Shortly thereafter, vane array 15 will pass through vane array 14 and begin to approach vane array 12, thereby narrowing the waveguide 25 as before.

It is possible to incorporate a second axial array of dipoles such as array 16, and in an airborne system, for example, dipole array 11 may be used to produce a beam which looks down while dipole array 16 is used to feed a dish reflector for long range scanning.

The means for feeding the electromagnetic energy into the space between inner. cylinder 31 and outer cylinder 21 will now' be explained. The feed waveguide 40, having a normal rectangular cross-section has its broad walls curved as it approaches the scanner. This is illustrated in Figs. 2 and 3, which showthe relation between the feed waveguide 40 and the scanners variable dimensions waveguide 25. The scanner can be fed from either or both ends, the feed for only one end being shown.

The moving rows of vanes 13,15 and 17, which are straight throughout the length of the dipole array 11, are set in at an angle, at either end of the scanner, the taper at one'end being shown in Figs. 1 and 3. This effectively tapers the width of waveguide 25 from that of feed waveguide 40 to the narrowest useful dimension in the scanner.

Similarly, one or more of the fixed rows of vanes 12 and 14 are set in at an angle, at either end of the. scanner, I

to taper the width of waveguide 25 from that of feed guide 40 to the widest useful dimension. At intermediate positions the width of waveguide 25 tapers first wider then narrower, corresponding to the portions of the fixed taper and the movable taper that are exposed to the fields inside the guide 25. At no point of the scan is there a discontinuity in the guide width, which changes gradually,

thuspreserving a match at the-input and outputends of the scanner It is also possible to feed each of the waveguides included between adjacent stationary vane arrays 14 and 14A, 14A and 14B, and 14B and .12, corresponding to the waveguide included between vane arrays 14 and 12', in the same manner'that waveguide 25 is fed. It is further possible to incorporate with each of the abovementioned additional waveguides, a dipole array similar to the array 11. For example, as shown in Figs. 1, 2 and 3, waveguide 26 is fed by a waveguide 42 and is coupled to an antenna dipole array 16 in the same manner that waveguide 25 is fed by waveguide and is coupled to array 11.

An example of a use for a scanner employing a plurality of waveguides and antenna arrays, such as waveguides 25 and 26 and arrays 11 and 16, is an airborne system wherein array 11 may be used to produce a beam ofelectromagnetic energy for scanning in a vertical, downward direction While at the same time array 16 may be used to produce a second beam for long range scanning in a forward direction.

The present invention herein described provides a means whereby the beam of electromagnetic energy from a linear array may be conveniently scanned with great rapidity and uniformity.

The frequency at which a beam of electromagnetic energy is scanned between two limits is determined directly by the speed of rotation of the inner assembly 30.

Thus, it is to be clearly understood that the description and illustrations of the invention made above has been given only by the way of example and not as a limitation on the scope of the invention as set forth in the objects and the accompanying claims.

What is claimed is:

1. A rotary scanner, comprising an outer stationary cylindrical conductive assembly having a plurality of internally projecting vanes, said vanes being arranged in a plurality of arrays, an array of dipoles disposed at predetermined intervals along the outer surface of said outer assembly, an inner rotating assembly comprising, a cylindrical conductive member having a plurality of externally projecting vanes, said vanes being arranged in a plurality of arrays to provide a variable dimension waveguide between said inner and said outer assemblies, said vanes in said arrays on said inner assembly and said outer assembly being disposed in such manner to allow said array of vanes on said inner assembly to pass through said array of vanes on said outer assembly, said array of vanes on said rotating member thereby gradually varying the wide dimension of said guide as said inner assembly rotates.

'2. The combination of claim 1 wherein said rotary scanner includes a plurality of variable dimension waveguides fed by a plurality of feed waveguides, a plurality of dipole arrays, said dipole arrays disposed for simultaneously propagating and sweeping a plurality of beams of electromagnetic energy. 7

3. A waveguide with first and second broad walls spaced apart by a predetermined fixed distance and first and second narrow walls, the width of said waveguide as measured between narrow walls being adjustable, said waveguide comprising, a first conductive member forming said first broad wall, first and second arrays of conductive vanes projecting out from said first conductive member and defining said first and second narrow walls at the maximum width of said waveguide, a second conductive member forming said second broad wall, a third array of conductive vanes projecting out from said second conductive member and defining one of said narrow walls at widths of said waveguide less than said maximum and means for mounting said second conductive member and said third array of vanes for retraceable movement along a path everywhere equidistant from said first conductive member, said third array of vanes being oriented with respect to said first and second arrays of vanes so as to allow the passage ofsaid thirdarray of vanes through said first and second arrays of vanes.

4. A waveguide having first and second broad walls spaced apart by a predetermined fixed distance and first and second narrow walls, the width of said waveguide as measured between said narrow walls being adjustable, said waveguide comprising a first conductive'member forming said first broad wall, first and second means mechanically and electrically secured to said first conductive member and defining, respectively, said first and second narrow walls at the maximum width of said [waveguide, a fourth conductive member forming saidsecond broad wall and fifth conductive means mechanically and electrically secured to said fourth conductive member and defining one of said narrow walls at widths of said waveguide less than said maximum, said fourth conductive member being movable along a path everywhere equidistant from' said first conductive member whereby =the width of said waveguide is adjustable. V 1

5. A waveguide having first and second broad walls and first and second narrow walls, comprising, a first variable-width section and a second constant-width sec tion serial connected to said first section, said first section of said waveguide having a width, as measured be: tween its narrow walls, that is adjustable, said waveguide at its first section comprising, a first conductive member secured to said second section and forming the first broad wall of said first section, first and second means mechanically and electrically secured to said first conductive member and defining, respectively, said first and second narrow walls of said first section at the maximum width of said first section, said second narrow wall and said first broad wall of said firstsection being substantially linear continuations of said second narrow wall and said first broad wall, respectively, of said second section, said first narrow wall of said first section at the widest dimension of said first section providing said first section with a maximum wide dimension substantially greater than the corresponding wide dimension of said second section, said first narrow wall of said first section at the widest dimension of said, first sectionbeing gradually tapered in the region of the junction of said first and second sections so that the width of said first section at its maximum width gradually decreases'from said maximum width to the width of said second section, a second conductive member forming said second broad wall of said first section, said second broad wall of said first section being substantially a linear continuation of said second broad wall of said section section, means mechanically and electrically secured to said second conductive member defining, in combination with said first means, said first narrow wall of said first section at widths of said first section less than said maximum, said first narrow wall of said first section at widths of said first section less than said maximum being gradually tapered in a'direction awayfrom said second narrow .wall in the region of said junction so as to increase the width of said first section except as limited by said first means, and means for movably mounting said second conductive member along a path everywhere equidistant from said first conductive member. I

6. A waveguide having first and second broad wallsand first and second narrow walls comprising, a first variablewidth section and a second constant-width section serially connected to said first section, said first section having a width, asmeasured between its-narrow walls, that is adjustable, said first section comprising, a first conductive member secured to said second section and forming the first broad wall of said first section, a plurality of vanes projecting outwardly from said first conductive memberfsaid vanes being arranged in first and second arrays defining, respectively, said first and second mar row walls of said first section at the maximum width of said first section, said first broad wall of 'said first section and said second narrow wall of said first section being substantially linear extensions respectively of said of said first broad wall and second narrow wall of said second section, said first narrow wall of said first section at the maximum width of said first section being gradually tapered in the region of the junction of said first and second sections so that the width of said first section gradually decreases from its' maximum width to the width between the narrow walls of said second section, a second conductive member forming said second broad wall of said first section, said second broad wall being substantially a linear extension of said second broad wall of said second section, a plurality of vanes projecting outwardly from said second conductive member, means for mounting said second conductive member for movement relative to said first conductive member along a path everywhere equidistant from said first conductive member, said vanes on said first and second conductive members being disposed in a manner to allow said vanes on said second conductive member to pass through said vanes on said first conductive member, said vanes of said second conductive member defining, in combination with said first array of vanes of said first conductive member, said first narrow wall of said first section at widths less than said maximum, said first narrow wall at widths less than said maximum tapering gradually in a direction away from said second narrow wall of said first section except as limited by said first array of vanes so that there is an absence of a Sharp discontinuity in the configuration of the efiective walls of said waveguide independently of the width of said waveguide.

7. Apparatus of claim 6 and an array of antenna elements coupled to said first variable Width-section of waveguide and disposed along the length thereof.

8. A wave guide assembly comprising, in combination, a pair of concentric cylindrical conductors, the outer conductor of said pair having at least two spaced longitudinal arrays of rectangular conducting vanes projecting from its inner surface, said arrays including a first group of vanes having equal areas with corresponding sides in vertical alignment and a second group of vanes having successively greater areas with one of their sides stepped in a first direction by increasingly greater amounts from corresponding sides of said first group whereby said arrays form in combination with portions of the inner surface of said outer conductor and the outer surface of said inner conductor a first wave guide member having a linear length of uniform width followed by a length of tapered width, a'third longitudinal array of rectangular conducting vanes extending from the outer surfaces of said inner conductor, the individual vanes of said third array being longitudinally offset with respect to corresponding vanes of said spaced longitudinal arrays, said third array including a first series of vanes of equal areas with corresponding sides in vertical alignment and a second series of vanes having their respective sides offset by increasing greater amounts from corresponding sides of said first series of vanes in a direction opposite to said first direction, and a second wave guide member coupled to said cylindrical conductors and adapted to supply electromagnetic energy to said first wave guide member.

9. A wave guide assembly comprising, in combination, a pair of concentric cylindrical conductors, the outer conductor of said pair having first and second parallely spaced longitudinal arrays of rectangular conducting vanes projecting from its inner surface, said arrays forming in combination with portions of the inner surface of said outer conductor and the outer surface of said inner conductor a first wave guide member of fixed dimensions, a third longitudinal array of rectangular conducting vanes projecting from the outer surface of said inner conductor, the individual vanes of said third array being longitudinally offset with respect to corresponding vanes of said first and second arrays such that the vanes of said third array pass between adjacent vanes of said first and second arrays upon relative rotation of said conductors Whereby the dimensions of said first wave guide member are varied, a second wave guide member coupled to said cylindrical conductors and adapted to supply electromagnetic energy to said first wave guide member, and means for maintaining an impedance match between said second wave guide member and said first wave guide member as the dimensions of the latter are varied, said means including auxiliary vanes added to said first and second arrays and stepped in a first direction and auxiliary vanes added to said third array and stepped in a direction op posite to said first direction.

References Cited in the file of this patent UNITED STATES PATENTS 2,413,085 Tiley Dec. 24, 1946 2,433,368 Johnson et al. Dec. 30, 1947 2,446,863 Yevick Aug. 10, 1948 2,453,414 De Vore Nov. 9, 1948 2,480,208 Alvarez Aug. 30, 1949 2,521,844 Gordy Sept. 12, 1950 2,699,501 Young Jan. 11, 1955 2,704,327 Chandler Mar. 15, 1955 

